1. Field of the Invention
The present invention relates to a contact pin utilized for a socket for electrical parts for detachably accommodating and holding an electrical part such as a semiconductor device (called as xe2x80x9cIC packagexe2x80x9d hereinlater), and also related to a socket for electrical parts provided with such contact pin.
2. Related Art of the Invention
In a known art, there has been provided an IC socket, as xe2x80x9csocket for electrical partsxe2x80x9d mentioned above, for carrying out performance test of an IC package as xe2x80x9celectrical partxe2x80x9d, which is preliminarily disposed on a printed circuit board and in which an IC package is accommodated in this IC socket to thereby establish an electrical connection between the IC package and the printed circuit board.
As such IC package, there is provided one having, for example, a rectangular body having a side portion from which a number of terminals extend sideways.
Under the state that the IC package is accommodated in the IC socket, when contact portions of contact pins of the IC socket contact to a number of terminals of the IC package, respectively, the terminals and the printed circuit board are electrically connected through the contact pins.
Such contact pin is formed by being punched out from a metal thin plate having conductivity, by means of press working, so as to have an elastic portion, which is elastically deformed by being pressed by an operation member which is vertically movable and a contact portion formed to a front (top) end side of the elastic portion and adapted to contact the terminal of the IC package.
When the IC package is accommodated in the IC socket, the operation member is lowered. The operation member is formed with a cam portion which presses a contact piece of the contact pin to thereby elastically deform the elastic portion and retire the contact portion of the contact pin from an insertion range of the terminal of the IC package.
Under the state mentioned above, the IC package is accommodated in an accommodation portion of an IC socket body, and thereafter, the operation member is moved upward. According to this upward movement, the contact portion of the contact pin returns to its initial position by the elastic force of the elastic portion thereof, and the contact portion is then contacted to an upper surface of the terminal of the IC package to thereby establish the electrical connection therebetween.
However, in the known structure mentioned above, there may cause a case that a rough or course cut surface may be provided at the time of punching out the contact pin from the metal thin plate, and, in such case, according to the repeated operation of accommodation or removal of the IC package, the elastic portion of the contact pin may be loaded repeatedly and a stress is concentrated on a corner portion thereof by the coarse surface of the elastic portion, thus facilitating fatigue and making worse its durability.
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a contact pin used for a socket for electrical parts having an improved structure of an elastic portion of the contact pin and also provide a socket for electrical parts having such improved contact pin.
This and other objects can be achieved according to the present invention by providing, in one aspect, a contact pin for an electrical part formed from a metal material having conductivity, comprising:
an elastic portion elastically deformable; and
a contact portion formed to a tip end portion of the elastic portion and adapted to contact a terminal of an electrical part,
wherein the elastic portion is polished by polishing means.
According to this aspect, the elastic portion of the contact pin is formed to have a smooth surface by the polishing means, so that a load is not concentrated at a specific portion even if the load is repeatedly applied, and hence, the durability of the contact pin can be improved.
In a preferred embodiment of this aspect, the polishing is performed, such as chemical polishing, without applying any external force. A nickel plating may be effected to the elastic portion to which the chemical polishing has been made.
The elastic portion is formed to provide a curved shape.
According to the preferred embodiment mentioned above, the contact pin even being small in size and weak in strength can be polished, by such as chemical polishing, by applying no external mechanical force. According to the chemical polishing treatment, a number of contact pins can be polished at the same time by, for example, dipping them in a polishing solution, thus improving the workability for manufacturing the contact pins. The nickel plating will compensate the reduction in thickness of the contact pin including the elastic portion through the polishing treatment and, hence, the elastic strength of the elastic portion will be maintained.
In a modified aspect of the present invention in the above aspect, there is provided a contact pin for a socket for an electrical part formed from a conductive material, comprising:
a base portion;
a stationary piece extending from the base portion and contacting the electrical part; and
a movable piece extending from the base portion and contacting the electrical part,
wherein the movable piece comprises an elastic portion and a movable contact portion contacting the electrical part and the elastic portion is polished.
In this aspect, the chemical polishing treatment will be preferably applied. The chemical polishing is effected so that the movable contact portion has a surface roughness of a value less than a predetermined value.
In another aspect, the contact pin of the present invention is applied to a socket for an electrical part, and the socket for an electrical part having a terminal comprising:
a socket body to which an electrical part is mounted;
an operation member provided for the socket body to be vertically movable in an operative state, the operation member being formed with a cam portion;
a contact pin provided for the socket body, the contact pin formed from a metal material having a conductivity and comprising an elastic portion elastically deformable, a contact portion formed to a tip end portion of the elastic portion and adapted to contact the terminal of an electrical part, and an operation piece to be pressed by the cam portion of the operation member,
wherein the elastic portion is polished by polishing means, and the elastic portion is elastically deformed when the operation member is moved downward and the operation piece of the contact pin is pressed by the cam portion of the operation member to thereby separate the movable contact portion from the terminal of the electrical part.
The socket is an IC socket provided with a number of contact pins and the electrical part is an IC package provided with a number of IC leads as the terminals.
The nature and further characteristic features of the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings.